血红蛋白需要几个肽链？（）
A、3.0
B、4.0
C、5.0
D、6.0
参考答案：B
Lily with her parents ______ Oxfam since two years ago.
A．has joined
B．have joined
C．has been in
D．have been in
族群认同（Ethnicidentity）
